Securities Available for Sale - Expected Maturities of Available-for-Sale Securities (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Amortized cost
Securities available-for-sale, amortized cost	$ 1,049,932
Fair value
Securities available for sale, at fair value	1,032,868
Debt Securities Excluding Mortgage-Based Securities
Amortized cost
One year or less	797
More than one year to five years	50,131
More than five years to ten years	59,373
More than ten years	5,000
Securities available-for-sale, amortized cost	115,301
Fair value
One year or less	797
More than one year to five years	49,613
More than five years to ten years	57,971
More than ten years	4,480
Securities available for sale, at fair value	112,861
Mortgage-backed securities and collateralized mortgage obligations
Amortized cost
Securities available-for-sale, amortized cost	934,631
Fair value
Securities available for sale, at fair value	$ 920,007

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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